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19 17 









Arthur G. Fitzner and Walter Wollaston 









MAY 31, 1917 



PAUL V. galvin library ^;2^U^s.r-.Yc..t:^^^SS^^ 

35 WEST 33RD STREET -^ ' 

CHICAGO, IL 60616 .- D^ac'cf Engin«H„g S.udies 

Dran of Cultural Sludi. 

Picric Acid from Ohlorbenzol. 



Preface 3 

Introduction 4 

Theoretical Considerations ...... 6 

The Process 11 

Experimental Work 13 

1. First Nitration. 13 

2. Hydrolysis 26 

3. Liberation of Dinitrophenol 

from its Sodium Salt ...... 29 

4. Final Nitration 32 

Summary 37 

Appendis: 40 

Selected Bibliography 40 


Ho.l^' Apparatus for Nitration and 

Hydrolysis 14 

No.2i,' Apparatus for Steam Distill- 
ation 28 

Picric Acid from ClilorTDenzol. 


This investigation into the production 
of picric acid from monochlorhenzol was 
undertsiken "because of the lack of literature 
on the subject although the process is knoTOi 
to he in extensive use. Owing to the very 
limited amount of time which was available 
for this work the experimenters were obliged 
to confine their efforts to the application 
of a certain series of reactions which appear- 
ed to be most practical. As the attainment of 
maximum yields at all stages was esseatial to 
the success of the process considerable attent- 
ion was paid to this phase of the work. 

The authors desire to express their grati- 
tude for the valuable assistance rendered and 
interest shown throughout the work by Prof. 
Harry McGormack. 

Picric Acid from Ohlorbenzol, 


Owing to the present international situa- 
tion the use of picric acid as an explosive has 
increased enormously. It is also used to a 
very limited extent in the dye industry "but 
other yellow dyes have heen found which are 
less costly. 

Picric Acid is the most powerful explo- 
sive known and is therefore used extensively 
as the bursting charge of shells. The pure 
acid is exploded only hy means of a priming 
charge such as a cap of mercury fulminate, hut 
when traces of its metallic salts are present 
it is easily exploded hy detonation. Because 
of this fact great care must he taken in its 
manufacture and use to prevent contamination. 

The usual method for the manufacture of 
picric acid is to nitrate phenol which has 
heen previously sulphonated. With this process 
it is impossible to obtain a sufficiently 

Picric Acid from ChlorlDenzol. 

pure product without recryatallization, "but 
with the ehlorhenzol process the loss due to 
this operation is eliminated hecause of the 
high purity of the picric acid originally 

Picric Acid from Chlortenzol, 

Theoretical Considerations. 
^en monochlorbenzol is su'bjected to 
strong nitration such as with a mixture of 
concentrated or fuming nitric and sulphuric 
acids at a moderately high temperature, the 
resulting product is largely dinitrochlor- 
henzol. It is impossihle to ohtain trinitro- 
chlorhenzol by direct nitration, and "because 
of this fact the production of this hody as 
an intermediate could not he considered. The 
first product of the nitration of chlorhenzol 
consists of a mixture of ortho, meta, and 
para mononitrochlorhenzols. The reaction 
proceeds as follows: 

C5H5CI ± HNO3 = C^H^CKUOg) * Hj,0 

The three isomers have the following structural 
formulae : 

Picric Acid from Chlorbenzol. 

ortho meta para 
The amount of meta mononitrochlor"benzol 
formed is less than one percent and can "be 
neglected. The ortho and para derivatives are 
formed in nearly equal quantities, the exact 
amounts of each depending upon the temperature. 
The physical properties of the ortho and para 
mononitrochlorhenzols are tabulated "below: 


sp .gr . 








Both forms are insoluble in water hut 

Picric Acid from Chlorbenzol. 

soluble in alcohol and ether. They are hyd- 
rolyzed "by caustic soda solution only under 
pressure at 130°. 

After all of the chlorhenzol has heen 
converted to the mononitrochlorhenzols the 
action continues with the production of di- 
nitrochlor "benzol. The reaction proceeds as 
fallows : 

2 no; 

The main constituent of this nitration 
product consists of 1:2:4 dinitrochlorhenzol, 
the amount of the other possible isomers heing 
limited on account of the small quantity of 
meta mononitrochlorhenzol entering into the 
reaction. The physical properties of the 
1 :2 :4 dinitrochlorhenzol are as follows :, 1.697^^°: m.p., 53.5°: h.p.. 315°: 
crystalline form, trimetric crystals: in- 

Picric Acid from Chlorbenzol. 

solulDle in water, very slightly soluble in 
cold alcohol, very soluhle in hot alcohol and 

At ordinary pressure and at moderate tem- 
perature dinitrochlorhenzol is quantitatively 
converted into sodium dinitrophenate hy the 
action of caustic soda solution. The reaction 
proceeds as follows : 


-h^ NaOH' 




The sodium dinitrophenate is converted 
into the dinitrophenol hy acidification; 

-h IS/a^SO* 

The physical properties of dinitrophenol 
are as follows:, 1.683^^ : m.p., 114°: 
crystalline form, yellow tablets: solubility 
in water at 20°, 5 grams per 100 cc : soluble 


Picrio Acid from CJhlorbenzol. 

in aloohol and ether. Dinitrophenol may be 
easily converted into trinitrophenol or picric 
acid by moderately strong nitration. The reaction 
is as follows : 



The physical properties of picric acid 
arexas follows:, 1.767: m.p., 122.5°: 
crystalline form, yellow leaf: moderately 
soluble in alcohol and ether. Its solubility 
in water greatly increases with an increase 
in temperature as is shown in the following 
table : 

Temperature an_. ?icric_per_100cc_., water 

OOQ. .67 

20 1.10 

60 2.77 

80 4.22 

100 6.75 


Picric Acid from Chlor"benzol . 

Owing to the facility with which mono- 
chlorhenzol is converted into 1:2:4 dinitrochlor- 
henzol and the ease with Y;hich the chlorine 
of the latter hody is replaced by hydroxyl "by 
means of caustic soda solution, the following 
process for the production of picric acid 
from chlorhenzol was decided upon as being the 
most practical: 

The steps involved are given below: 

1. The conversion of chlorbenzol to 1:2:4 di- 
nitrochlorbenzol . 

2. The hydrolysis of dinitrochlorbenzol to 
sodium dinitrophenate . 

3. The liberation of dinitrophenol from its 
sodium salt. 

4. The nitration of dinitrophenol to picric 

In carrying out the above reactions the 
experimenters attempted to determine the most 


Picric Acid from Chlorbenzol 
economical means of production. 


Picric Acid from Chlorbenzol. 


The experimental work was carried out in 
four divisions corresponding to the four steps 
in the process as outlined on page 11. 
1. nitration. 

The apparatus used in the nitration of 
the chlorhenzol is shown in Photo Ho .1 on p. 14, 
It consisted of a two liter flask supported 
hy an iron stand and provided with a water 
cooled vertical condenser. Heat was supplied 
hy means of an oil hath heated hy a Bunsen 
burner, and agitation was effected hy "blowing 
a slow steady stream of air in at the hase of 
the flask hy means of a tube inserted through 
the condenser. Thermometers were used both in 
the outside bath and in the nitration mixture. 
At first considerable difficulty was encount- 
ered in obtaining a cork or rubber stoppe* 
which would withstand the attacks of the 
strong hot vapors during one entire period 


Picric Acid from Chlorbenzol, 

Photo Ho.l. 
^paratua for 
ITitration and Hydrolysis, 


Picric Acid from Ch.lor'benzol . 

of nitration. Several innovations were tried 
among them "being gold foil, lead foil, and 
cement protective coatings. Of these a bar- 
ium sulphate-sodium silicate cement proved 
to "be the "best. A cork stopper was first 
hored and fitted for the condenser, thermometer 
and flask, the flask end "being made somewhat un- 
size so as to allow for a heavy layer of the 
cement. The condenser and thermometer were 
inserted in the cork and a thick layer of the 
cement forming paste was applied and allow- 
ed to harden. The cork was then sealed to 
the flask with fresh cement. Such a cork 
withstood the disintegrating influences of 
all subsequent nitrations. Temperature reg- 
ulation was easily controlled by not allov/- 
ing the temperature of the outer bath to 
exceed that of the nitration mizture by more 
than 20*^ at any time. 


Pioric Acid from ChlorlDenzol . 

Tlie nitration of. the chlorbenzol was eff- 
ected by the use of several nitrating mixtures. 
The possibility of a quantitative production 
of dinitrochlorhenzol by means of ordinary 
nitric ( 1.42) and sulphuric ( 
1.84) acids was eliminated since the work of 
Louis Sabinovitz and A.A.Wells : The Chemical 
Engineer, Feb. -Mar., 1917, p. 24 , conclusive- 
ly proved that only small amounts of dinitro- 
chlorbenzol were formed under such conditions 
even at elevated temperatures (200°0.). 

Accordingly the first nitration was made 
with a mixture of ordinary nitric ( .1.42! 
and fuming sulphuric ( 1.93, 20 fo free 
3O3) acids. An excess of 25fo over the theore- 
tical amount of nitric acid was used and suff- 
icient sulphuric acid was added to bring the 
water content of the final waste acid to about 
20^,^. After assuming several ratios of 
chlorbenzol to sulphuric acid, it was found 


Picric Acid from Chlortenzol. 

that with a proportion of 1 to 3 this water 
content was approximated. A smaple calcu- 
lation is given helow: 

CgHp-Cl * 2 HITOJ5 = CgHjjCKlIOj,)^ * 2 H2O 

112.5 126 202.5 36 

Assuming 100 grams of chlorbenzol, the amount 
of nitric acid ( 1,42,70^) theoretical- 
I7 required is : 

126/112.5 X IO0/.7 " 160 gms. miOg { 70^;^) 
With 25fo excess - 200 gms. " " 

Water in 200 gms. acid equals: 

200 X .3 =60 gms. water 

Water formed in the reaction equals : 

36/112.5 X 100 = 32 gms. water 

The amount of water absorhed by the 300 gms., 
of fuming sulphuric is : 

SO3 X HgO = SgSO^ 

80 18 98 


Picric Acid from Chlorlienzol. 

300 X .20 X 18/80 = 13.5 gms. water a"bs. 
The amount of water in the spent acid mixture is 

( 60 i 32) - 13.5 = 78.5 gms. water 
The total weight of spent acid is : 

HgSO^(ioo::^)(30o i 13.5) :: 313.5 gms. 

Water = 78.5 gms. 

xs Em^{100fo){4:0x,'7) = 28.0 gms. 

Total ~ 420.0 gms. 
Percent of water in the acid mixture equals : 

100 X 78.5/420 = 18.7 % water 
In this calculation the possible loss due to 
the escape of uncondensed vapors has "been 

The first nitration was therefore made with 
200 gms. chlorhenzol 
400 gms. KEO^i 1.42) 
600 gms. HpSO^ ( 1.93) 
fhe two acids were poured into the flask and 
the mixture cooled. The chlorhenzol was then 


Picric Acid from Chlorbenzol . 

slowly added to the acid mixture with continual 
shaking and cooling. The flask was then sealed 
to the condenser. The mixture was continually 
agitated "by air and heated sufficiently to 
maintain a moderate reaction. The following 
is a tahle of the time and temperature through- 
out the operation : 



2:00 P.M. 



100° c. 















Throughout the run there was a slight evolution 
of hrown NOg fumes hut the amount of these was 
never allowed to become great. Mien the reaction 


Picric Acid from ChlorT)enzol. 

had ceased , after about four hours, the par- 
affin hath was removed and the contents of the 
flask allowed to cool slightly. The oily layer 
of dinitrochlorbenzol was separated from the 
waste acids in a separating funnel, and was 
subsequently washed several times with hot 
water until free from acid. The acid mixture 
was diluted with water to precipitate dissolved 
dinitrochlorbenzol, and the flaky crystals 
were coagulated as an oil by heating. This 
portion was added to the main bullr v/hich upon 
cooling to room temperature solidified. The 
total yield of washed product was 345 grams. 
Further work with this product showed that it 
contained 10',^ of mononitrochlorbenzols . The 
theoretical yield of dinitrochlorbenzol from 
200 grams of chlorbenzol is : 

202.5/112.5 x 200 = 355.5 gms. 
The actual yield of dinitrochlorbenzol was : 

345 z .9 = 310.5 gms. 


Picric Acid from ChlorlDenzol. 

The percent of the theoretical yield was there- 
fore : 

100 s 310.5/355.5 = 87 .4 f5 

IJitration with Fuming Acids, 
In order to obtain a greater yield of the 
dinitrochlorhenzol a stronger nitration mix- 
ture was used, the water content of the spent 
acid being calculated to he about i5^. The 
charge taken which corresponded to these 
conditions was as follows : 

200 gms . chlorbenzol 
400 3BS. HHO_^( 1.465, 8lfo) 
600 gms. HgSO^ { 1.93, 20^ 30^ ) 
The treatment was very similiar to the prev- 
ious Ijiitr at ion. The log of the run was-. 
Time_ Temperature^ 

12 :30 Start 

1:00 llOOC. 

1:30 125° 








Picric Acid from Chlorbenzol, 








The dinitrochlorlDenzol was separated from the 
waste acid in a manner similiar to that used 
in the previously nitration. The total yield of 
mixed nitrochlorhenzols was 35E gms., of which 
1^ was later found to he monochlorhenzols. 
The percent of the theoretical yield was : 

100 X .99 X 35Z/355.5 = 98 ^ of dinitro- 

chlorhenzol . 
On a similiar run with slight variations in time 
and temperature of nitration suhstantially the 
same results were obtained . 


Picric Acid from Chlorbenzol . 

Nitration with ^aMO^ and H2SO4. 
Another method of keeping the water content 
of the spent nitration acid mixture down to a 
minimum is- to produce the nitrdic acid during 
the reaction hy the action of sulphuric acid 
( 1.42) on crude sodium nitrate. A few 
calculations with various proportions of 
chlorhenzol, sodium nitrate, and ordinary- 
sulphuric acid showed that it was not practical 
to reduce the water content of the waste acid 
mixture helow ZOfo as too much sulphuric would 
he required. Accordingly in order to influence 
the reaction to a greater yield of dinitrochlor- 
henzol a greater excess of nitric acid was 
employed , this time 100^ excess. The amount of 
sulphuric acid used was calculated to reduce the 
water content of the final waste acid to ahout 
20fo, To satisfy these conditions the following 
proportions were used: 


Picric Acid from Chlorbenzol. 

100 gms • ehlorlDenzol 
300 gms. sodium nitrate 
600 gms. H2SO4 ( 1.84, 93fo) 
The operations were very much like those 
in the two previous nitrations except that at 
the "beginning of the reaction more careful 
temperature control was required "because of 
the tendency of the action to "become violent. 
The data taken from such a run was as follows 



11:30 A.M. 























Picric Acid from Chlorbenzol. 

While the contents of the flask were still hot, 
the oily layer of dinitrochlorhenzol was decant- 
ed off into a heaker of col* water. The sodium 
sulphate and acid residue was cooled by the 
addifcion of sufficient cold water to dissolve 
all of the sodium sulphate, all dinitrochlor- 
henzol which it contained was coagulated as 
an oil. This was added to the main bulk of the 
oil which was then washed and allowed to 
solidify as in the previous nitrations. The 
yield of the crude product was 177 gms., and 
since ifo was later found to be mononitrochlor- 
benzols, the yield of dinitrochlorbenzols was 
175.2 gms. The percent of the theoretical yield 
of dinitrochlorbenzol was therefore : 
100 X 175.2/355.5/2 r 98.6 5$ 
As the sodium nitrate meltod was obviously 
the cheapest of the three methods used and the 
yield was high, it seems to be most adaptable to 


Picric Acid from Ghlorbenzol, 

the process, 

The apparatus used, in the hydrolysis of 
the 1:E:4 dinitrochlorhenzol obtained by the 
nitration of chlorbenzol was exactly the sazne 
as that used in the nitration. A s caustic 
soda solution readily reacted with the dinitro- 
<h lorbenzol to form sodium dinitrophenate, no 
other hydrolyzing reagents were used but 
several variations of the concentration of the 
alkali and of the temperature were studied. 
The amount of UaOH was calculated as follows : 
C6H3C1(1I02)2 * 2 NaOH = CeHgCOUa )(II02 )2 SJaCl 
202.5 80 * H2O 

Therefore 100 x 80/202.5 = 39.5 gms., UaOH 
are required. In all of the experiments 45 gms., 
were used. The ratios of UaOH to water which 
were used were 1-5,1-8,1-10,1-12, and 1-14. 
Very little difficulty was encountered in ob- 
taining a complete hydrolysis when the contents 


Picric Acid from Chlortenzol . 

of the flask was kept at just a boiling tem- 
perature, hut in all cases there was a forma- 
tion of tarry todies sufficient to discolor the 
product . The formation of tarry matter by the 
decomposition of the :^enate was probably due 
to the more intense hydrolyzing conditions at 
the start. Accordingly more cautious and slow 
heating at the start of the reaction resulted 
in, in the case of the dilute solutions off 
caustic soda, a product that was practically 
free from tarry bodies. 

The solution of sodium dinitrophenate at 
this stage was contaminated by small amounts 
of unhydrolyzed mononitrochlorbenzols, and it 
was found that these could easily be driven off 
by steam distillation. A description of the 
apparatus used is hardly necessary as Photo ITo.E 
on page 28 shows all the essential details. A 
steam bath was used under the flask containing 


Piorie Acid from flhlorbenzol , 

Photo II0.2. 
Apparatus for 
Steam Distillation. 


Picric Acid from dilortienzol . 

the sodium dinitrophenate solution so as to 
keep the contents near lOO^C, hut yet not high 
enough to decompose the phenate into tarry 
"bodies. The mononitrochlorhenzols distilling off 
were weighed and checked against the nitration 
operation to which they corresponded. As the 
mononitrochlorhenzols have the odor of nitro- 
benzene the end of the distillation was easily 
detected by the ahsebce of that odor. The 
warm sodium dinitrophenate solution was then 
filtered in order to free it from a small 
amount of insoluble impurities. 
The next main reaction, which was the 
liberation of dinitrophenol from its soditm 
salt solution, was accomplished by acidification, 
The equation for this change has been given 
elsewhere • Since ', 


Picric Acid from Chlorbenzol. 

ZQ^E^Olimzlz- 2C7H3{0H)(lI02)2-lHgS0^ S2HCL 
405 368 98 72.9 

The amount of sulphuric acid Mvhich is required 
to literate the dinitrophenol from the sodium 
salt solution fonned by the hydrolysis of 100 
grams ( which was the charge used in all of 
the hydrolyses ) of dinitrochlorhenzol is: 
100 X 98/405 = 24.2 gms . H2SO4 
24.2/1.84Z .93 = l4.3 cc .HgS04{l .84 ) 
Because of the excess of caustic soda used in 
the hydrolysis, 20 cc, of acid were used. 
■When the concentrated acid was added to the 
slightly cooled phenate solution or visa versa, 
a very dark brown dinitrophenol contaminated 
with considerable tarry matter was obtained. 
After making various changes, a light yellow 
dinitrophenol precipitate was finally obtained 
by slowly adding the cooled phenate solution, 
with continual stirring, to an iced 10^ sulph- 
uric acid solution. Even with this procedure it 


Picric Acid from Ghlorbenzol . 

was found iinpossi"ble to precipitate a light 
colored dinitrophenol from a phenate solution 
which had "been contaminated with tarry matter 
during the hydrolysis of the dinitrochlor- 
benzol, hut with careful working and the oh- 
servance of the proper conditions at all steps 
an excellent light yellow dinitrophenol was 
always obtained. The precipitated dinitrophenol 
was filtered and largely freed from water by 
means of suction. The product Jims washed vTith 
cold water. The partially dried phenol was 
further dried on a porous plate in a steaip 
closet. The theoretical yield of dinitrophenol 
from 100 grams of dinitrochlorbenzol is 
( see top of previous page ) : 

100 X 368/405 = 90.8 gms. 
The actual yield varied from as low as 66 gms., 
in the case of the dark dinitrophenol to about 
95 grams in the case of the good color dinitro- 
phenol. On account of the difficulty of drying 
the efficiency of the process at this step 


Picric Acid from Chlorbenzol . 

could not te accurately determined. As would be 
expected greater yields of dinitrophenol ■S7ere 
obtained from the 99;o dinitrochlorbenzol than 
from the 90fj. The process did not require the 
dinitrophenol to he thoroughly dried, the dry- 
ing having been made to give some idea of the 
efficiency of the hydrolysis and acidification 

Ab was indicated on page 11, the last step 
in the process has for its object the conversion 
of the dinitrophenol obtained in the third step 
to trinitrophenol or picric acid. The apparatus 
used for this nitration was similiar to that 
used in the nitration of the chlorbenzol. The 
condenser, however, was not essential on 
account of the comparatively low temperatures 
{ up to llO^C. ) employed. The nitration was 
carried out v/ith ordinary nitric acid( 
1.42, 70^). 


Picric Acid from Chlorbenzoi. 


CgH3(0H)(II0g)g * HNO3 = CgH3(0H){II0g)3 * HgO 
184 63 229 18 

the amount of acid required for 1 gn,, of di- 
nitrophenol is; 

63/184 = ,342 gm. HIIO3 

or .342/. 7 - .488 gm. HITO3 (SOg) 
In the nitration ICO^ excess of nitric was used 
and sufficient sulphuric acid ( 1.84) 
wasoadded to make the water content of the 
waste acid about ZOfj, The proportions of 
dinitrophenol, nitric, and sulphuric which 
gave these conditions were 1:1:2 respective- 
ly. The calculations are omitted as similiar 
ones have already been given. The charge was 
agitated and the temperature gradually raised 
in order to maintain the reaction. After about 
three hours the reaction was apparently com- 
pleted and the temperature had risen to about 
115° G# The hot mixture was then poured into 
3 or 4 times its volume of cold water. 


Picric Acid from dilortenzol. 

This gave a dense crystalline precipitate 
of picric acid which was light yellow in color. 
TS/hen cold the picric acid was filtered off, 
washed with cold water, and dried on a porous 
plate in a warm closet. With light colored 
dinitrophenol very good picric acid having 
a melting point in the neighborhood of 1E0°C., 
was ohtained without recrystallization, hut it 
was not possible to obtain a good picric acid 
from a darlr dinitrophenol by such a procedure. 
Eecrystallization from water gave the acid 
in the form of beautiful yellow leaves. The 
theoretical yield of picric acid from 100 grains 
of dinitrophenol from the equation at the top 
of the previous page is : 

100 X 229/184 ' 124.4 ^s. 
In one run v/here the charge consisted of: 
100 gms. crude dinitrophenol from 100 gms., 

of 90f5 dinitrochlorbenzol. 
100 gms. HUO^C 1.42) 


Piorio Acid from Chlortienzol . 

200 gms. H2SO4 { 1.84) 
a yield of 82 grams of picric acid was ob- 
tained : 

100 X.9 X 229/202.5 = 101.7 gms. picric 

The combined efficiency of the hydrolysis, 
acidification, and final nitration operations 
was : 

82/101.7 = 80.6 7^ 

The average efficiency of each of these three 

operations was therefore : 

rsO X 100 xlOO = 93.0 $ 

In another rim 80 grams of picric acid 
was obtained from 90 grams of a total of 95 
grains of crude dinitrophenol obtained from 
100 gms., of 99'^ dinitrochlorbenzol. The 
Theoretical yield would have been: 

100 z .99 X229/202.5 x 90/95 = 106.0 ^s. 
The combined efficiency of the three steps was ; 
80/106 IE 75.4 fi 


Picric Acid from ChlorlDenzol . 
The average efficiency of each step was therefore 

^75 .4 z 100x100 ~ = 91.0 ^J 

In the two runs above the best possible 
conditions were attained at all steps. The di- 
nitrophenol used was practically free from 
tarry matter and the picric acid obtained was 
of excellent color. In other runs where darker 
dinitrophenol was employed the yields were 
considerably less than those ginen above. 

Picric Acid from Chlorbenzol. 


The results obtained throughout the exper- 
iments on the production of picric acid from 
monochlorhenzol on a small scale were consid- 
ered very favorable^ and there is every reason 
to think that the results could he easily 
duplicated or possibly surpassed in large scale 
operations. Since the yield of dinitrochlor- 
benzol from chlorbenzol in the first step of 
the process was 98^ of the theoretical and as 
the combined efficiency of the other three steps, 
involving tne nydrolysis of the dinitrochlor- 
bensol to sodium dmltropneuate, the acidifica- 
tion of the latter to dinitrophenol, and the 
nitration of the dinitrophenol to picric acid, 
was from 75. 4^5 to 80.6^, the overall efficiency 
or percent of the theoretical yield of picric 
acid from chlorbenzol was: from 74^ to 79v3. 
Considering the number of operations involved 
in the process, this recovery can be regarded 


Picric Acid from Clilorbenzol, 

as excellent as it makes the average effic- 
iency of each operation from 
^ 74xLooxl00xl00 



V 792:100x!Ii00s:100 = 94.3^ 

In the ordinary phenol process 190 parts 
of picric acid are obtained from 100 parts of 
phenol, which makes the recovery about lofo 
of the theoretical. In the absence of authentic 
data on the costs of production of picric acid 
in the phenol process and the difficulty of 
estimating the costs in the chlorbenzol pro- 
cess, a real rigid comparison of the two 
methods is impossible. With the latest quet- 
ations of phenol at 42^^ per lb,, and chlorbenzol 
at 309^ per lb., and the costs of other chemicals 
used in the two processes being approximately 
the same, the other factors of the cost of 
production could be slightly in favor of the 


Picric Acid from GhlorlDenzol. 

phenol process and still allow a sufficient 
margin on the side of the chlor'oenzol process 
to permit competition. 


Picric Acid from Chlorbenzol, 

Selected Bibliography. 

DrwA. H.Sey, Snythetlc Phenol and PlcridJ Acid, 
Metallurgical and Chemical Sngineering, 
Vol. XIII, Oct. 1,1':^15, p. 6b6-690. 

C.Ellls.L.Rabinovitz .A.A.VJells, The '^reparation 
of Picric Acid and other titrated Phenols, 
The Chemical Engineer, Feb. -aar. ,1917 , p. 21-5. 

Kurt H.Mayer and Fredrich Bergius , Preparation 
of Phenol from Chlorbenzol, Chemical Abs- 
tracts. Vol. y. 1915. D.52?-62tt.